The present invention is directed to an engine fuel delivery management system for an internal combustion engine. In particular, this invention is directed to a system and method that compensates for a change in engine operating state by altering an amount of an operating parameter, such as quantity of fuel to be delivered.
It is believed that the performance of an internal combustion engine is dependent on a number of factors including the operating cycle (e.g., two-stroke having 360 degrees of crankshaft rotation per cycle, four-stroke having 720 degrees of crankshaft rotation per cycle, or Wankel), the fuel type (e.g., gasoline or diesel) the number and design of combustion chambers, the selection and control of ignition and fuel delivery systems, and the ambient conditions in which the engine operates.
Examples of design choices for a combustion chamber are believed to include choosing a compression ratio and choosing the numbers of intake and exhaust valves associated with each chamber. In general, it is believed that these choices cannot be changed so as to calibrate engine operation after the engine has been built.
With regard to ignition systems, breaker point systems and electronic ignition systems are known. It is believed that these known systems provide spark timing based on an operating characteristic of the engine, e.g., speed of rotation and load. In the case of breaker point systems, it is believed that engine speed is frequently detected mechanically using centrifugally displaced weights, and that intake manifold pressure or exhaust manifold pressure is commonly used to detect engine load. In the case of electronic ignition systems, it is believed that engine speed is generally detected with an angular motion sensor associated with rotation of the crankshaft, and that engine load is frequently detected, for example, by the output of a throttle position sensor, intake manifold pressure or mass airflow sensor. In each case, spark timing is typically fixed for a given steady operating state of the engine.
With regard to fuel delivery systems, carburetors and fuel injection systems are known. It is believed that those known systems supply a quantity of fuel, e.g., gasoline and air, in accordance with the position of the throttle as set by the operator. In the case of carburetors, it is believed that fuel is delivered by a system of orifices, known as xe2x80x9cjets.xe2x80x9d As examples of carburetor operation, it is believed that an idle jet may supply fuel downstream of a throttle valve at engine idling speeds, and that fuel delivery may be boosted by an accelerator pump to facilitate rapid increases in engine load. It is believed that most carburetors must be disassembled and different size jets or pumps installed to modify the amount of fuel delivery at a particular engine load. However, that is a laborious process that, it is believed, most often, can only be done while the engine is not running.
It is believed that known fuel injection systems, which can be operated electronically, spray a precisely metered amount of fuel into the intake system or directly into the combustion cylinder. The fuel quantity is believed to be determined by a controller based on the state of the engine and a data table known as a xe2x80x9cmapxe2x80x9d or xe2x80x9clook-up table.xe2x80x9d It is believed that the map includes a collection of possible values or xe2x80x9csetpointsxe2x80x9d for each of at least one independent variable (i.e., a characteristic of the state of the engine), which can be measured by a sensor connected to the controller, and a collection of corresponding control values, for a dependent variable control function, e.g., fuel quantity.
Conventionally, it is believed that maps are developed by the engine manufacturer and permanently set in an engine control unit at the factory. Currently, for on-road vehicles, this is believed to be legally required in order to meet emissions regulations. However, it is believed that even when it is not legally required, the manufacturers prevent engine operators from modifying the maps for a variety of reasons, such as the manufacturers believe that their maps provide the best engine performance, the manufacturers are concerned that an engine operator might damage the engine by specifying inappropriate control values, or the manufacturers assume that an engine operator might not have sufficient skill to properly modify a map. However, it is believed that the manufacturers have xe2x80x9coptimizedxe2x80x9d their maps to perform best under a set of conditions that they specify. In certain cases, however, it is believed that those conditions do not match the conditions in which the engine is operated. Consequently, stock maps sometimes limit, rather than optimize, an engine""s performance.
Conventional maps, furthermore, are typically created to provide fuel delivery and ignition timing suitable for the engine when operating at a steady-state. Thus, map values may not be appropriate for an engine operating in transition such as, for example, an accelerating or decelerating engine.
Further, engine performance is believed to be substantially dependent on how combustion is accomplished in the ambient conditions. The stoichiometric mass fraction ratio of air to gasoline is approximately 14.7:1. However, it is believed that ratios from about 10:1 to about 20:1 will combust, and that it is often desirable to adjust the air-fuel ratio (xe2x80x9cAFRxe2x80x9d) to achieve specific engine performance (e.g., a certain level of power output, better fuel economy, or reduced emissions). Properly calibrating the fuel delivery system of an engine to deliver the optimum AFR under all operating conditions is one of the most important goals of a calibration effort. It is also frequently the most time consuming, difficult, and costly part of the calibration effort. Similarly, it is also believed to be desirable to adjust ignition timing, commonly measured in degrees of crank rotation before a piston reaches top-dead-center of the compression stroke, to achieve specific engine performance (e.g., lowest fuel consumption or reduced emissions).
It is believed to be a disadvantage of known ignition timing systems and fuel delivery systems that engine operation is constrained by the fixed controls established by the suppliers of these systems. It is also believed that a simple, effective system and method for varying fuel delivery during engine operating state transitions is needed. Thus, there is believed to be a need to overcome the disadvantages of known fuel delivery systems.
The present invention is directed to a system, method and apparatus for adjusting a quantity of fuel delivered to an engine when an engine operating state transitions. In accordance with one form of the present invention, there is provided such a method that includes determining from a data table a current steady-state quantity of fuel to be delivered to the engine under a steady-state condition and adding a transitory quantity of fuel to the current steady-state quantity of fuel. The transitory quantity of fuel is based on a difference between a previous steady-state quantity of fuel delivered and the current steady-state quantity of fuel to be delivered. The steady-state quantity of fuel is a quantity of fuel delivered or to be delivered to an engine when the engine is operating at any steady-state. The data table from which the steady-state quantity of fuel is determined may be a two-dimensional map utilizing engine load and engine speed to determine steady-state fuel quantity. The steady-state quantity determined may be the closest value on the map corresponding to an engine operating state that is retrieved and used as the required steady-state fuel mass required. Alternately, the steady-state value may be interpolated from multiple values on the map. For example, when interpolation is used the steady-state value may be interpolated from the two speed values closest to the current engine operating state and the two load values closest to the current engine operating state. A transition occurs when an engine shifts from one operating state to another. A transition may, therefore, correspond to any movement from any one position to any other position on a map. Compensation for transitions resulting in both positive and negative transitory fuel quantities may be implemented and different weights may be placed on positive and negative transitory fuel quantities.
The present invention is also directed to an engine transitional fuel control apparatus and method of operating that apparatus. The engine transitional fuel control apparatus includes a processor, a fuel supply device; and a fuel supply actuator. The processor has an output and a memory, whereby the memory contains a fuel delivery table and instructions. When executed by the processor, the instructions cause the processor to determine a steady-state amount of fuel to be delivered, add a transitory quantity of fuel to the steady-state amount of fuel to be delivered for a period of time following initiation of the transition, and apply a signal corresponding to that total amount of fuel to the output. The steady-state amount of fuel to be delivered is determined by reference to the fuel delivery table and the transitory quantity of fuel is based on a difference between a previously determined steady-state quantity of fuel and the current steady-state amount of fuel to be delivered. The fuel supply actuator is coupled to the output of the processor and operably coupled to the fuel supply device to control fuel flow therethrough.
The present invention provides a number of advantages including the ability for fuel delivery to be adjusted electronically without need for component removal or system disassembly. Another advantage is the ability of the present invention to electronically adjust fuel delivery, including specifically transitory fuel quantity, while the engine is running. Yet another advantage is that fuel supply to an engine can be controlled by way of a program that compensates for changes in engine operating state. Another advantage is that fuel supply to an engine can be controlled by way of a program that compensates for desired changes in engine operation.
Accordingly, the present invention provides solutions to the shortcomings of prior engine control systems and methods. Those of ordinary skill in the art will readily appreciate, therefore, that those and other details, features, and advantages of the present invention will become further apparent in the following detailed description of the preferred embodiments of the invention.